The present invention relates to cosmetic and personal care compositions, such as hair styling compositions, containing block copolymers, and to their use in the treatment of hair.
Cosmetic and personal care compositions such as hair styling sprays, mousses, gels, shampoos and conditioners, frequently contain resins, gums and adhesive polymers to provide a variety of benefits, for example, film-forming ability, thickening, sensory properties and hair shaping and setting.
Polymers for use in such compositions are usually linear or graft homo- or co-polymers which contain various monomers in an alternating, random manner.
Graft copolymers are known for use as film-forming polymers in hair care and other personal care compositions. These graft copolymers typically comprise a polymeric backbone and one or more macromonomers grafted to the backbone, in which the physical and chemical attributes such as glass transition temperature and water solubility can be selected independently for the polymeric backbone and macromonomer grafts in order to provide the desired overall polymer properties.
For example, WO95/01383 and WO95/01384 describe the use of water or alcohol soluble or dispersible graft copolymers in hair and skin care compositions, in which the copolymer has a backbone and two or more polymeric side chains, and is formed by copolymerisation of randomly repeating monomer units A and B. Monomer A is selected to have a hydrophobic character and macromonomer B comprises a long hydrophilic part. EP-A-0412704, EP-A-0408313 and EP-A-0412707 have suggested the use of silicone grafted acrylate copolymers in hair care applications. U.S. Pat. No. 4,988,506 describes the use of non-pressure sensitive polysiloxane-grafted copolymers in hair care compositions. U.S. Pat. No. 5,986,015 describes graft copolymers and hair care compositions containing them.
Block copolymers have an advantage over graft copolymers in that the polymer architecture can be controlled more readily. This is particularly important when designing polymers with segments of distinct physical and chemical properties for particular applications. Graft copolymers typically have many side chains and are not characterised as block copolymers.
WO 98/53794 discusses (AB)n block copolymers, where A is a silicone block and B is a vinylic block. U.S. Pat. No. 5,271,930 (Fintex Inc) describes benzoate esters of polyalkoxylated block copolymers, such as PLURONICS(trademark), for skin and hair care compositions. U.S. Pat. No. 5,472,686 and U.S. Pat. No. 5,660,819 (both Nippon Unicar) describe non-hydrolysing block copolymers comprising a linear polysiloxane-polyoxyalkylene block as a repeating unit in cosmetic formulations. U.S. Pat. No. 5,965,115 and U.S. Pat. No. 5,972,356 (both Procter and Gamble) describe the use of silicone-polyoxyalkylene copolymer surfactants for improving stability of a polyorganosilicone emulsion in personal care compositions.
ABA triblock copolymers where the A blocks are hard and the B block is soft, are generally referred to as xe2x80x9cthermoplastic elastomersxe2x80x9d. Such polymers are multiphase compositions in which the phases are intimately dispersed. A well known material of this type is, for example, poly(styrene-b-butadiene-b-styrene) commonly known as Kraton(trademark) and available from Shell Chemicals Company. However, these materials are only soluble in common organic solvents such as toluene and they are not soluble in cosmetically acceptable solvents such as water and ethanol.
U.S. Pat. No. 5,980,878 discloses thermoplastic elastomers for use in hair and skin care compositions which have a backbone polymer and a plurality of polymeric side chains bound along the length of the backbone polymer. The polymers described, which have a backbone and a plurality of pendant polymer chains, are effectively graft copolymers.
International applications numbers PCT/EP00/04225 and PCT/EP00/04429 describe polysiloxane block copolymers which are built up from units of the formula [A] and [B], in which A is a polymeric block built up from radically polymerisable monomer and B is a polysiloxane block. The block copolymers may be used in cosmetic and personal care compositions.
GB 1425228 discloses hair spray or setting lotions containing ABA block copolymers. The polymers are water insoluble and organic solvents are required in the compositions in order to solubilise the polymers. In all of the examples given, the A blocks are poly(2-vinyl pyridine) and a typical B block is polybutadiene.
Compositions suitable for application to the hair containing two-block or three-block copolymers are described in GB 1512280. The polymers contain an A block which is a homopolymer obtained from the polymerisation of an amino-substituted methacrylate ester, optionally quaternised. In all of the examples, an organic solvent, such as an alcohol, is required in order to solubilise the polymer and there is no suggestion in the document that the copolymers would be soluble in water.
It is an object of the present invention to provide cosmetic and personal care compositions which exhibit advantages over the compositions of the prior art. In particular, the invention aims to provide a novel class of polymers for use in cosmetic and personal care compositions. The invention involves compositions containing polymers which can be produced relatively readily, and which have properties that can be tailored to the particular application. The hair treatment compositions of the invention which are useful for styling hair may have advantages in terms of longer lasting hold and/or improved feel.
In a first aspect, the present invention provides a cosmetic or personal care composition comprising a thermoplastic elastomer which is a block copolymer comprising a core polymer having a backbone comprising at least a proportion of Cxe2x80x94C bonds and two or more flanking polymers, each flanking polymer being covalently bound to an end of the core polymer, wherein the copolymer is soluble at a level of at least 1% by weight in water at 25xc2x0 C., and a cosmetically acceptable diluent or carrier.
Further provided by the invention in a second aspect is a cosmetic method of treating hair which comprises applying to the hair a composition of the invention.
In a third aspect, the invention provides the use of a composition of the invention for the cosmetic treatment of hair.